Pulsars presents microcontroller based beverage dispensing machine, model pmv 5100. It has a time setting method. Here the water levels in the boiler and tank are sensed periodically by means of conductive probes and the valves are opened accordingly. By a special time splice method, the sensing is done for such short durations at appropriate times, so that rusting of the probes is completely avoided. A high power dc power supply board accompanies this unit to power 12 v dc valves. No of relays: 4 - two for the powder motors and two for the whipper motors, no of transistors: 3 - two for water valves and one for constant head valve. Sequence of operation: ready led glows at the start of the cycle. When ready is pressed, the two leds for coffee and tea glow and the ready led goes off. The constant head valve is opened after checking the level sensors during this time. When the user selects coffee or tea by pressing the corresponding switch, the following events happen. Led of the selected drink glows. The other led is off. Corresponding water valve and powder motor operate for set times. Constant head valve opens when the second level sensor is out of water. When the water covers the top level sensor in the boiler, chv is closed. Raedy led is on and the machine is ready for next cycle. An advantage of this system is that whenever the water level in the boiler goes below the third level sensor, the microprocessor detects it at the time of checking any water level sensor and switches off the heater relay, thereby avoiding damage to the heater coil.
